Celestial Motion - Boris Boguslavsky

Celestial
Motion
The Hubble Ultra-Deep Field is a longexposure photograph of a small part of the sky
taken over the course of five months by the
Hubble Space Telescope.
The area of the sky photographed is about 3
arcminutes across. This is just one-tenth of
the diameter of the full Moon as viewed from
Earth, smaller than a 1 mm by 1 mm square
of paper held at 1 meter away, and equal to
roughly one thirteen-millionth of the total area
of the sky.
The majority of the lights in this photo are
entire galaxies, each containing billions of
stars. There are about ten thousand galaxies in
the Hubble Ultra-Deep Field.
This is arguably one of the most important and
humbling photographs ever taken.
MOVEMENT IN THE COSMOS
THE NATURE
OF GRAVITY
MARS
THE MOON
URANUS
NEPTUNE
EARTH
SATURN
VENUS
JUPITER
MERCURY
F=G
( )
m1 x m2
r2
F is the force from gravity.
G is the gravitational constant.
m1 and m2 are the masses of the bodies.
r is the distance between their centers.
NEWTONS FIRST LAW OF MOTION
WHAT IS GRAVITY?
SPEED IS RELATIVE
GRAVITATIONAL WELLS
.
MEASURING
GRAVITY WITH ISAAC NEWTON’S .LAW OF UNIVERSAL GRAVITATION
Isaac Newton’s first law of motion states
that an object in motion will stay in motion
unless acted upon by an outside force.
This also applies to objects at rest. Objects
in space move because a force acted on
them, or is acting on them. This is one of
the core principles of physics and is vital to
understanding motion.
Gravity is a force that is responsible for
a large portion of motion in the universe.
The gravitational force is one of the four
fundamental forces of physics, and acts by
pulling all matter together. Gravity is actually
the weakest of the four forces. The reason
that we notice it so much is because gravity
works over long distances and is always
attractive. The more mass an object has, the
larger the gravitational force it exerts on other
objects.
Another important concept to understand is
that we have no way to measure absolute
speed. Speed is completely relative to us.
Humans can only detect acceleration, and can
only measure speed relative to something
else.
Every object has a gravitational well. This well
is a conceptual model of the gravitational
field that surrounds a body of matter. The
more massive the body, the deeper and more
extensive the well. Things on the surface of
the body are at the bottom of the well, and as
they leave the body’s atmosphere and escape
its gravitational field, they climb out of the
well. The deeper the well, the more energy it
takes to escape.
Isaac Newton was the first to accurately
describe an equation that could calculate
the force from gravity. The gravitational force
between two objects is directly proportional
to the product of their masses and inversely
proportional to the square of the distance
between them.
This equation is called Newton’s law of
universal gravitation. This law has since been
superceded by Einstein’s theory of general
relativity, but it is still used as an excellent
approximation of the effects of gravity.
Relativity is only necessary when dealing with
extremely massive and dense objects, such
as black holes, or when there is a need for
extreme precision.
THE NATURE
OF ORBITS
THE SHAPE OF ORBITS
Orbits vary in their shape. They can be
elliptical, or almost perfectly circular. The
moon’s orbit of the earth is slightly elliptical.
The earth is at one foci of this orbital ellipse,
while the other foci is empty.
balanced orbit
low velocity
high velocity
PERPETUAL FREEFALL
EQUAL AREAS IN EQUAL TIMES
We all know that the moon orbits the sun, but
what a lot of people seem to misunderstand
is the nature of an orbit. When an object is
orbiting around another object, that object is
in freefall.
The closer an object is to whatever it’s
orbiting, the faster it will travel. Johannes
Kepler observed an interesting relationship
in orbital physics, which is known as the
Second Law of Kepler. It states that an object,
following its orbital path, sweeps out equal
areas in equal times.
However, it has a velocity perpendicular to the
object that it is orbiting. At the right velocity,
this means that the object will essentially stay
in freefall indefinitely. If the velocity is too
high, the orbiting object will break out of the
orbit and fly off into space. Too low, and the
object will crash into whatever it’s orbiting.
The orbiting object travels faster when it is
closer to a source of gravity, so both blue lines
in the diagram took the object equal times to
travel across, even though they are of different
length.
The second law of Kepler states that the grey
wedges drawn by those lines are of equal
areas. This is what is meant by “equal areas in
equal times.”
mass
diameter
1.90x1027 kg
139822 km
mass
diameter
5.69x1026 kg
116464 km
mass
diameter
mass
diameter
MERCURY
3.30x1023 kg
4879 km
mass
diameter
4.87x1024 kg
12104 km
VENUS
mass
diameter
EARTH
5.98x1024 kg
12742 km
mass
diameter
MARS
JUPITER
There are eight planets in our solar system.
The four closest to the sun are terrestrial
planets (rocky planets), and the four farthest
form the sun are jovian gas giants. This is
because the gas from which they were
formed could only condense into harder
elements under more heat. All of the planets
orbit the sun in the same plane and in the
same direction. This is due to how solar
systems are formed.
mass
diameter
6.42x1023 kg
6779 km
URANUS
OUR NEIGHBORS
8.68x1025 kg
50724 km
SATURN
NEPTUNE
1.02x1026 kg
49244 km
SOLAR SYSTEM
FORMATION
Tiny particles around the star
began condensing from the
gas. Collisions between these
particles let them grow and
attract even more particles.
These were the seeds of our
planets.
A cloud of interstellar gas
becomes slightly too dense and
very slowly begins contracting
because of its own gravity. It gets
more dense and contracts faster.
The contraction is non-uniform, so
the cloud starts spinning.
Eventually, the clouds of gas
at the center of the disc were
heated to 10 million Kelvin.
Nuclear fusion began and our
sun was born as a star.
The disk stops contracting
due to reaching gravitational
equilibrium and begins to lose
heat in the form of infrared
radiation.
The spinning cause the
cloud to take on a disk-like
shape. Most of the matter is
concentrated near the center
of the disk. Colliding particles
from the contraction generate
heat.
THE MILKY WAY
The milky way galaxy - our home galaxy - is
a barred spiral galaxy. It has two arms that
extend and reach around its center. Near
the middle, there is a bar-shaped structure
that is composed of stars. The milky way
is 100,000-200,000 light years in diameter
and contains 200-400 billion stars. Many of
these stars have planets of their own. These
are incomprehensibly large numbers. Some
analogies help put them into frame.
If the sun were the size of a grapefruit, the
earth would be the size of the head of a
pin, and they would be 16 meters apart.
Pluto would be 539 meters away from
the sun.
If the whole solar system out to pluto was
the size of a US quarter, our milky way galaxy would be about the size of the United
States of America.
Our solar system is about two-thirds of the
way out from the galactic center, on the inner
edge of a spiral. It takes about 200 million
years for the sun to complete a revolution
around the center of the galaxy. The galaxy as
a whole is traveling as well.
Galaxies are formed in much the same way
as solar systems, just on a much, much larger
scale. Instead of forming a star at the center,
there is enough mass and gravity to form a
black hole.
Our solar system is just one star among
millions in one galaxy among millions more,
and it’s all plummenting through space.
Typefaces used:
Univers LT 45 Light
Univers LT 65 Bold
Univers LT 59 Ultra Condensed
Garamond Premiere Pro Semibold Italic
Sources:
wikipedia.org
nasa.gov
universtoday.com
Illustrated and written by Boris Boguslavsky